EFFECTS OF PHOSPHORUS CONCENTRATION ON Cu, Zn, Fe AND Mn UTILIZATION BY WHEAT

Abstract

Greenhouse studies were conducted in which various amounts of phosphorus were added to calcareous and noncalcareous soils, and the iron, manganese, zinc and copper utilization by wheat were determined. Wheat yields were significantly increased by phosphorus fertilization; mean yields on the noncalcareous soils were greater than on the calcareous soils. Plant micro-element concentration and uptake were reduced in many instances when large amounts of phosphorus were applied. Plants grown on the calcareous and noncalcareous soils had similar concentrations of iron, manganese and copper. However, plants grown on the calcareous soils tended to contain lower amounts of zinc than plants grown on the noncalcareous soils. Concentration of micro-elements in soil-water extracts of phosphated soils, particularly for the noncalcareous soils treated with large amounts of phosphorus, tended to be greater than for nonphosphated soils. Yields were usually not affected when phosphorus at 2–100 ppm was added to nutrient solutions. Zinc and copper concentration and uptake were usually greater for plants grown in a 2-ppm phosphorus solution than for plants grown in solutions of higher concentration. In several instances, plant iron concentration and uptake were also reduced by high phosphorus concentration. Manganese uptake appeared not to be affected by phosphorus concentration. Increasing the micro-element concentration of nutrient solutions at various phosphorus concentrations did not affect yields but increased plant micro-element concentration and uptake, indicating that ion antagonism was mainly responsible for the lower utilization of microelements in high phosphorus media.